Orlistat is a reversible inhibitor of intestinal lipases, which is FDA indicated for obesity. It works by preventing the absorption of dietary fat intake. Lorcaserin, which is also indicated for the treatment of obesity, works by making a person feel full quicker and by decreasing their food intake via stimulation of the selective serotonin 2C receptors.
In a meta-analysis conducted by Chilton et al, the efficacy of orlistat vs. lorcaserin in people who are overweight/obese was analyzed. Studies included in the meta-analysis consisted of trials that "compared orlistat or lorcaserin to lifestyle advice (standard care), placebo, sibutramine, rimonabant or metformin and collected information on waist circumference change or withdrawals due to adverse events (AEs)." From this data, a mixed-treatment comparison was done.
Results of the meta-analysis showed orlistat’s efficacy to surmount that of the placebo and standard care when it came to decreasing waist size at 6 and 12 months. As for lorcaserin, it was found to be the best intervention to reduce waist circumference at 12 months (-2.45 cm). After a year of follow-up, it was seen that 5-6% of patients discontinued using orlistat or lorcaserin due to adverse events.
The authors concluded the study by recommending orlistat as adjunct therapy for obesity. They also mention that orlistat and lorcaserin are similar in efficacy and safety, when taken at the appropriate dose.
Chilton M et al. The effect of antiobesity drugs on waist circumference: a mixed treatment comparison. Diabetes, Obesity and Metabolism. 2013. Abstract. DOI: 10.1111/dom.12198